A vehicle subframe is such that longitudinal and transverse tubular members are joined together to thereby form, for example, a structure having the shape of projecting parallels and needed mount portions are formed on the structure, and there is known, for example, a subframe in which cylindrical members are joined to ends of longitudinal and transverse members for attachment to a body. (Refer, for example, to JP-A-2003-146240 (hereinafter, referred to as Patent Document No. 1) (Page 4, FIG. 1)).
Patent Document No. 1 will be described based on the following figure.
FIG. 22 is an explanatory diagram which explains a basic configuration of the related art. A conventional automotive subframe is such that collar members 1302 are joined to distal end portions of a subframe main body 1301 for connecting the subframe to a body frame of a motor vehicle, and in the event that the subframe main body 1301 lacks in dimension, flat portions 1303 of the collar member 1302 are fillet welded (beads 1304) to the subframe main body 1301 in such a state that the flat portions 1303 are displaced as shown in (c).
In the automotive subframe of Patent Document No. 1, while the collar members 1302 at both ends of the subframe main body 1301 are fixed to the body and for example, a differential gearbox is mounted on the subframe main body 1301, the subframe main body 1301 is liable to be deformed, and there has been desired a structure which can increase the strength without interrupting the lightening of the weight of the subframe main body 1301.
In addition, in a bush mounting structure in which various types of members are mounted on a frame such as a body frame by brackets via elastic bushes, the elastic bush is made up of an inner tube, an outer tube which surrounds the inner tube and an elastic element which connects between the inner tube and the outer tube. There are known various types bush mounting structures like this (refer, for example, to Japanese Utility Model Registration No. 2601866 (hereinafter, referred to as Patent Document No. 2) (FIGS. 1 to 4)).
A conventional bush mounting structure shown in Patent Document No. 2 will be described based on the following figure, FIG. 21.
FIGS. 21(a), (b) are schematic diagrams of a conventional bush mounting structure, wherein FIG. 21(a) shows a side configuration of the bush mounting structure and FIG. 21(b) shows a cross-sectional configuration taken along the line b-b in FIG. 21(a).
This conventional bush mounting structure is such that left and right lateral linkages 303, 303 are mounted on a subframe 301 mounted on a body by a bracket 302 in such a manner as to swing. Elastic bushes 304, 304 are used at these mount portions to enable such a mounting.
As shown in FIG. 21(b), the subframe 301 is a pressed product which is formed into a downwardly oriented U-shape section component by joining together an upper half 305, which is placed upper, and a forward-placed front lower 306 and a rearward-placed rear lower 307 which are joined to a lower portion of the upper half 305.
The subframe 301 constructed as described above is such that a bracket, as a separate member, made up of a downwardly oriented U-shape section component is inserted to be mounted between a lower end portion of the front lower 306 and a lower end portion of the rear lower 307. The elastic bushes 304, 304 can be mounted on the subframe 301 by bolts 308, 308 which pass through the bracket 302, the lower end portion of the front lower 306 and the lower end portion of the rear lower 307.
Incidentally, the bracket 302 is required to sufficiently bear loads exerted thereon from axial and radial directions of the elastic bushes 304, 304, as well as transmitting the loads to the subframe 301 with good efficiency. To this end, the mounting strength and support rigidity of the bracket 302 on which the elastic bushes 304, 304 are mounted are wanted to be increased. Moreover, the bracket 302 is required to be simple in configuration.
As shown in FIG. 21(b), however, the aforesaid conventional bush mounting structure only constitutes a configuration in which the U-shape section bracket 302 is interposed between the front and rear lowers 306, 307. There still exists a room for improvement in attempting to increase the mounting strength and support rigidity of the bracket 302 on which the elastic bushes 304, 304 are mounted.